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Social Distancing of Symptomatic Cases within Households
as A Non-pharmaceutical Intervention

The world is gripped by the COVID-19 pandemic. An infected person, or index case, is likely to infect other people in their vicinity. Social distancing is touted as one of the main non-pharmaceutical interventions to minimize risk of infection. Current guidelines on nonpharmaceutical interventions advice symptomatic cases to stay in home isolation for 7-14 days. The question is whether this guideline puts their family members at increased risk.

It is vital to analyse the current pandemic to explore whether social distancing of symptomatic cases within households can minimize morbidity and mortality


  • Comprehensive contact tracing of COVID-19 in Taiwan showed an overall secondary clinical attack rate of 2.4%, but it was 8.5% among non-household family contacts and 13.6% among household contacts;
  • Studies from measles epidemics have shown that secondary cases within the same household suffer a 3-4 fold increased morbidity and mortality risk as a result of intensity of exposure.
  • Incidental reports of high case fatality rates within families from COVID-19 are being reported;
  • Repeated low-dose of virus influenza A in mice causes more severe disease with higher viral loads, increased lung inflammation, and mortality.
  • High levels of IL1-B upon repeated exposure with influenza A in animal models reflect the cytokine storm in critically ill patients with COVID-19;

The hypothesis is that secondary cases suffer more morbidity and mortality, because of higher and repeated infection load

Research Question
Do (secondary) cases with COVID-19 infection from larger households suffer higher morbidity and mortality than index cases?

Proposal for Data Analysis
Here we are starting an initiative to:

  • Collect aggregated statistics on case finding and households in specific regions e.g. regions in ItalyBrabant in the NetherlandsChina, etc.;
  • Calculate relative risks of morbidity and mortality;
  • Estimate primary and secondary attack rates;
  • Follow up of clinical cases for hospitalization, intensive care including use of respirator, and mortality;

Guidelines on home isolation of symptomatic cases as a non-pharmaceutical intervention need to be adapted

Contact when you want to contribute.

Update 22 March 2020

Rudi Westendorp, Thorkild Sørensen, Peter Aaby.

Dept Public Health, University of Copenhagen